Few eye problems cause more discomfort in dogs than the hereditary condition known as entropion. This is a problem that causes the eyelids to roll inward, pressing the eyelashes against the sensitive eye surface, and leading to pain, tearing and vision loss.

The lower lid is affected more often than the upper eyelid, although the condition can affect both. Entropion normally appears when the dog is young, before 1 year of age. Owners will notice their pet squinting, tearing excessively, avoiding bright lights and strong winds, and possibly pawing at its eyes or rubbing its face against the ground. The eyes also may appear red and irritated. As you can imagine, the pain of the lashes pressing against the sensitive cornea of the eye is significant. Over time, if the condition is not repaired, the cornea will be ulcerated and scarred, producing not only pain, but also reducing or destroying the dog's vision. Nerve damage also may occur within the eyelids and structures around the eye.

Most cases of entropion are genetically related. A second form, however, is known as "spastic entropion," and occurs when the eyelid rolls inward as the result of spastic contractions within specific eye muscles. This spastic action can result from a variety of causes, including injury, trauma and a muscular condition known as distichia. In rare cases, chronic untreated eye infections, such as severe conjunctivitis, can also cause the problem.

The only treatment for entropion is surgery, in which the affected eyelid is pulled outward and repositioned correctly, with the lashes well clear of the eye. Since the facial structure is still growing in young dogs, the procedure is often postponed until the dog is an adult, unless the condition is severe. In many cases, more than one operation may be required. A side note for owners -- although their health and vision may have been restored, dogs that have had surgery to correct entropion may not be exhibited in most show rings.

Entropion is a commonly inherited condition in many types of dogs. Selective breeding that is designed to produce animals with exaggerated facial features, such as prominent eyes and/or heavy facial folds, has worsened the problem in many breeds. Therefore it's recommended that would-be dog owners choose an animal with a more normal head conformation, especially if the animal is going to be used for breeding.

Entropion is particularly prevalent in the Basset Hound, Bloodhound, Chow Chow and Shar-Pei, and it is commonly found in giant breeds like Bernese Mountain Dogs, Great Danes, Mastiffs, Newfoundlands and Saint Bernards. Other affected breeds include the: Akita, Bulldog, Dalmatian, Irish Setters, Japanese Chin, Miniature Poodle, Old English Sheepdog, Pekingese, Pomeranian, Pug, Shih Tzu, Siberian Husky, Toy Poodle, Weimaraner and all types of Retrievers, Spaniels and Terriers.